In dynamoelectric machines such as motors and generators, the stationary field which interacts with the rotatable armature to convert electrical energy to mechanical energy, or to convert mechanical energy to electrical energy, is provided by coils of wire, known as field coils, which are disposed about field poles, for concentrating and directing the magnetic flux produced by the field coils. Field poles are generally configured as including a pole shoe, which has a concave contour matching the contour of the exterior of the armature, and overhangs the field coil, for trapping the field coil between the pole shoe and the motor frame to retain it in place. It has long been conventional to place a piece of insulating material having a generally rectangular outer periphery around the pole piece and against the motor frame, to protect the field coil from abrasion against the motor frame, and also to provide protection for the sides of the generally-rectangular field coils, to protect them from abrasion against the shoe portion of the pole piece and the sides of the pole piece. This is conventionally done by wrapping the coil with tape, even though one-piece insulators for field coils have long been known, such as that described in U.S. Pat. No. 1,797,768, issued to L. C. Goad on Mar. 24, 1931. Although functional, such structures have been difficult to produce properly and repeatedly, or have been inconvenient to use, and so have not found commercial acceptance.
The instant invention overcomes these and other deficiencies of the prior art.